Upper nozzle/plate integral unit and method of splitting the same

ABSTRACT

Disclosed is an upper nozzle/plate integral unit comprising an upper nozzle and an upper plate integrated together, which is capable of being easily split into the upper nozzle and the upper plate after use, while adequately maintaining a thickness of a joint between the upper nozzle and the upper plate during use. A metal casing  4  is bent inwardly along an outer peripheral surface of a lower end portion of an alumina carbon-based refractory body of the upper nozzle  1  to form a metal member. The metal member formed by bending the metal casing  4  inwardly has a length of 15 mm. A gap between the metal casing and the refractory body is filled with mortar having a thickness of about 0.5 mm. A recess  11  of the lower end portion of the upper nozzle  1  is fitted onto a raised portion  21  of the upper plate  2  through mortar, and the metal casing  4  of the upper nozzle  1  is in contact with a metal casing of the upper plate  2 . A peripheral edge of the metal casing of the upper plate  2  is fixedly joined to the metal casing  4  of the upper nozzle  1  through a plurality of welded portions  6.

TECHNICAL FIELD

The present invention relates to an upper nozzle/plate integral unit fora sliding nozzle assembly adapted to be attached to a bottom of a moltenmetal vessel, such as a tundish or ladle, and used for controlling aflow rate of molten metal, such as molten steel.

BACKGROUND ART

A sliding nozzle assembly comprises a plurality of refractory membersformed with respective nozzle holes and assembled together in such amanner as to be clamped at a high pressure, wherein at least one of therefractory members is adapted to be slidably moved so as to adjust anopening degree of a molten metal passage consisting of the nozzle holescommunicated with each other, to control a flow rate of molten metal,such as molten steel.

Typically, in cases where the sliding nozzle assembly is attached to atundish, five refractory members consisting of an upper nozzle, an upperplate, an intermediate plate, a lower plate and a lower nozzle, arearranged in this order in a downstream direction of a molten metalstream, although there is a type using no intermediate plate.

An operation of assembling such refractory members to form a slidingnozzle assembly is roughly classified into an on-site operation and anoff-site operation. The on-site operation means an operation ofattaching the refractory members to a bottom of a tundish while settinga metal frame in an open position, to form a sliding nozzle assembly onsite (i.e., in an on-site manner). The off-site operation means anoperation of replacing an entirety of a sliding nozzle assemblydetachably attached to a tundish (detachable-type sliding nozzleassembly), with a new one, wherein used refractory members of thedetached sliding nozzle assembly are replaced with new ones at alocation distant from the tundish (i.e., in an off-site manner).

The operation of assembling the refractory members to form a slidingnozzle assembly in an on-site manner is performed in the followingprocess. Firstly, the upper nozzle is applied with mortar on an outerperipheral surface thereof, and inserted into an inner hole of anozzle-seating brick inside a tundish. Then, the upper plate is pressedagainst a lower surface of the upper nozzle through a joint material,and fixed to a metal frame of the sliding nozzle assembly. Subsequently,the intermediate plate and the lower plate are fixed to the metal frame.Lastly, the lower nozzle is pressed against a lower surface of the lowerplate through a joint material, and fixed to the metal flame through abayonet coupling or the like.

As for the joint material, such as a shaped joint material or mortar, tobe placed between the upper nozzle and the upper plate and between thelower plate and the lower nozzle, it is necessary to accurately manage athickness of the joint material, preferably within control limits of ±1mm.

However, a joint between respective ones of the refractory members,particularly a joint between the upper nozzle and the upper plate, islikely to have a problem about a variation in thickness thereof, due tovariation factors, such as a position of the nozzle-seating brick, asize of the inner hole of the nozzle-seating brick, an outer diameter ofthe upper nozzle, an amount of the mortar applied onto the outerperipheral surface of the upper nozzle, and a hardness of the mortar. Ifthe thickness of the joint is excessively small, a gap will be likely tooccur around the joint during use. If the thickness of the joint isexcessively large, wear of the joint will be accelerated to increase arisk of molten metal leakage.

In the above situation, various techniques for replacing the refractorymembers have been proposed. For example, as a technique of replacingplates in an off-site manner, the following Patent Document 1 disclosesa technique of replacingly attaching a stationary plate and a slideplate fixed to a slide plate-supporting plate, to a retainer plateprovided on an outer shell of a ladle, while holding by a plate-handlingrod the stationary plate and a slide plate fixed to a slideplate-supporting plate.

Further, the following Patent Document 2 discloses a detachable-typesliding nozzle assembly adapted to be replaced by a slide-valvereplacement machine together with a slide-valve casing provided on abottom of a tundish. In the Patent Document 2, refractory members otherthan an upper nozzle, i.e., a slide valve (plate) and a lower nozzle,are replaced simultaneously. Specifically, the slide-valve casing isgripped and pulled out by a clamp arm attached to a replacementcarriage, and replaced with a slide-valve casing assembled with newrefractory members.

In this operation of replacing the refractory members, it is difficultto accurately manage a thickness of a joint between the upper nozzle andthe upper plate, not only in on-site replacement but also in off-sitereplacement.

As one of the measures against the above problem, the following PatentDocument 3 proposes an upper nozzle/plate integral unit comprising anupper nozzle and an upper plate integrated together without any jointtherebetween. Although this upper nozzle/plate integral unit is suitablefor simultaneously replacing an upper nozzle and an upper plate as in atundish, the upper nozzle is liable to rigidly stick to a molten metalvessel during repetitive use. Thus, if the upper nozzle/plate integralunit is used in the replacement system as disclosed in the PatentDocument 2, the stuck upper nozzle causes a problem about difficulty indetaching the sliding nozzle assembly from the tundish. Further, if theupper nozzle/plate integral unit is used in the type incapable of movingaway the retaining metal frame as disclosed in the Patent Document 1,the plates will conflict with the retaining metal frame to causedifficulty in pulling out and detaching the entire assembly.

-   -   [Patent Document 1] JP 05-318061A    -   [Patent Document 2] JP 06-000602A    -   [Patent Document 3] JP 05-507029A

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide an uppernozzle/plate integral unit comprising an upper nozzle and an upper plateintegrated together, which is usable in a sliding nozzle assembly, andcapable of being easily split into the upper nozzle and the upper plateafter use, while adequately maintaining a thickness of a joint betweenthe upper nozzle and the upper plate during use.

The present invention is made with a focus on a fact that, when an uppernozzle and an upper plate in a sliding nozzle assembly are fixedlyjoined together by a joining force which allows the upper nozzle and theupper plate to be easily disjoined from each other after use, whilemaintaining the joining during use together with other refractorymembers, instead of being fully fixed together, an obtained uppernozzle/plate integral unit can be easily split into the upper nozzle andthe upper plate, after use.

Specifically, the present invention provides an upper nozzle/plateintegral unit capable of being split into an upper nozzle and an upperplate and detached from a molten metal vessel, after use, wherein: theupper nozzle is in contact with the upper plate through a jointmaterial, in such a manner that respective nozzle holes of the uppernozzle and the upper plate are aligned with each other; the upper nozzlehas a metal member provided on a lower end portion thereof; and theupper plate has a metal sheet provided on an upper surface thereof,wherein the metal member of the upper nozzle is weldingly joined to themetal sheet of the upper plate at two or more positions, in such amanner that a weld leg is set in the range of 2 to 5 mm, and a totalweld length is set in the range of 5 to 60 mm.

In the upper nozzle/plate integral unit of the present invention, themetal member on the lower end portion of the upper nozzle is weldinglyjoined to the metal sheet on the upper surface of the upper plate at twoor more positions. That is, the upper nozzle is joined to the upperplate only by means similar to spot welding, i.e., only by a joiningforce which allows the upper nozzle and/or the upper plate to be easilydetached from a joined portion therebetween. Thus, in an operation ofreplacing refractory members, the upper nozzle/plate integral unit canbe easily split into the upper nozzle and the upper plate.

As a specific example of the metal member to be attached onto the lowerend portion of the upper nozzle, it is preferable to use a metal casingwhich covers an outer peripheral surface of an intermediate portion andthe lower end portion of the upper nozzle, or a metal band disposed onthe outer peripheral surface of the lower end portion of the uppernozzle, in view of capability to retain the upper nozzle in an attachedstate thereto.

As a specific example of the metal sheet to be attached onto the uppersurface of the upper plate, it is preferable to use a metal casing whichcovers a lateral surface and the upper surface of the upper plate, inview of capability to retain the upper plate in an attached statethereto. Alternatively, a doughnut disk-shaped metal sheet may beattached onto the upper surface of the upper plate. That is, the metalsheet of the upper plate in the present invention is provided as amember to be weldingly joined to the metal member on the lower endportion of the upper nozzle, and may be provided on at least a weldingarea of the upper surface of the upper plate. For example, the metalsheet may be a type formed by laminating a plurality of metal sheets, ormay be a type a part of which is buried in the upper surface of theupper plate. The metal casing which covers the lateral surface and theupper surface of the upper plate may be formed by providing a metal bandor hoop around the lateral surface of the upper plate, and welding ametal sheet covering the upper surface of the upper plate, to the metalband or hoop.

In an operation of welding between the upper nozzle and the upper plate,a weld leg is set in the range of 2 to 5 mm, and a total weld length isset in the range of 5 to 60 mm. If the weld leg is less than 2 mm, thewelding operation becomes technically difficult, and a joining force isliable to become insufficient. If the weld leg is greater than 5 mm, itbecomes an unrealistically large value as compared with a thickness ofthe metal member or sheet. If the total weld length is less than 5 mm,the upper nozzle/plate integral unit is liable to be unexpectedlydisjoined into the upper nozzle and the upper plate during handling. Ifthe total weld length is greater than 60 mm, the upper nozzle/plateintegral unit is liable to have difficult in being split into the uppernozzle and the upper plate after use. As used herein, the terms “weldleg” and “weld length” are defined, respectively, as a width S and alength L of a weld bead in a welded portion 6 between the upper nozzle 1and the upper plate 2, as shown in FIG. 1.

In the present invention, a method of splitting the upper nozzle/plateintegral unit into the upper nozzle and the upper plate may comprisepulling the upper plate or the sliding nozzle assembly from outside themolten metal vessel. In this case, a crowbar or the like may be used formanually scooping out the upper plate so as to pull the upper plate.Alternatively, a driving source, such as a hydraulic cylinder, may beused for pulling the upper plate or the sliding nozzle assembly.

Depending on a configuration of the upper nozzle or a mounting structurefor the upper nozzle, the above method may comprise pulling or pushingthe upper nozzle toward an inside of the molten metal vessel to detachthe upper nozzle from the welded portion. Further, solidified metal maybe pulled away from a bottom of the molten metal vessel to allow theupper nozzle to be detached together with the solidified metal.

In the above method, if a joining force based on welding is excessivelystrong, a pullout force required for detaching the upper nozzle and/orthe upper plate from the welded portion will be considerably increasedto cause a problem about difficulty in the detaching, and occurrence ofdistortion in the sliding nozzle assembly.

In order to prevent disjoining between the upper nozzle and the upperplate during transportation and during on-site handling, whilefacilitating detachment from the welded portion after use, a product Wof the weld leg S [mm] and the total weld length L2 [mm] is preferablyset in the range of 25 to 300. A condition that the product W is 25corresponds to a condition that a calculated value of the joining forcebased on welding is about 0.5 t (ton), and a condition that the productW is 300 corresponds to a condition that the calculated value of thejoining force based on welding is about 7 t. That is, if the product Wis less than 25, the joining force becomes insufficient, and the uppernozzle/plate integral unit is likely to be disjoined into the uppernozzle and the upper plate during transportation and during on-sitehandling. If the product W is greater than 300, a joining force becomesexcessively strong, which is likely to cause difficulty in detaching theupper nozzle and/or the upper plate from the welded portion, andoccurrence of distortion in the sliding nozzle assembly.

In the present invention, the upper nozzle and the upper plate arewelded together while ensuring a gap therebetween in advance. Thus, amortal joint between the upper nozzle and the upper plate can be formedat a constant thickness, and the joint thickness can be accuratelymanaged by a manufacturer or the like. This makes it possible toeliminate the risk of wear of the joint due to excessive increase injoint thickness, or the risk of abnormal refractory wear or molten metalleakage due to a gap caused by excessive decrease in joint thickness, soas to achieve a stable casting operation.

The upper nozzle/plate integral unit of the present invention issuitably used in a detachable-type sliding nozzle assembly. Thedetachable-type sliding nozzle assembly is pulled out after use, forexample, by the replacement carriage as disclosed in the Patent Document2. Thus, the upper nozzle and/or the upper plate can be detached fromthe welded portion therebetween by use of the pullout force. If thepullout force for the detachable-type sliding nozzle assembly isinsufficient, a driving force of a driving source, such as a motor or ahydraulic cylinder, may be additionally used. The upper nozzle/plateintegral unit installed in the detachable-type sliding nozzle assemblyalso has an advantage of allowing the upper nozzle to be mounted to themolten metal vessel in conjunction with an operation of attaching thedetachable-type sliding nozzle assembly to the molten metal vessel, soas to achieve enhanced operating efficiency.

The welding portion between the upper plate and the upper nozzle may bebroken by a hydraulic driving force of a hydraulic ram cylinderinterposed between a retaining metal frame of the detachable-typesliding nozzle assembly and the molten metal vessel. Thus, even when apullout force for the detachable-type sliding nozzle assembly isinsufficient, the detachable-type sliding nozzle assembly can bedetached from the molten metal vessel.

A retaining metal frame formed with a concave portion having a crowbarinsertion groove may be provided. In this case, the upper nozzle/plateintegral unit can be easily split into the upper nozzle and the upperplate by inserting a crowbar into the crowbar insertion groove, andmoving the crowbar to scoop out the upper plate. The use of a crowbarmakes it possible to split the upper nozzle/plate integral unit in asimple and easy manner based on the principle of leverage. Preferably,the upper nozzle/plate integral unit has a weld leg of 2 to 4 mm and atotal weld length of 10 to 20 mm to allow one person to perform thesplitting operation by himself/herself, using a crowbar having anadequate length.

Preferably, the product W of the weld leg S [mm] and the total weldlength L2 [mm] is set in the range of 25 to 100 to more facilitate thesplitting operation using a crowbar. A condition that the product W is25 corresponds to a condition that the calculated value of the joiningforce based on welding is about 0.5 t (ton), and a condition that theproduct W is 100 corresponds to a condition that the calculated value ofthe joining force based on welding is about 2 t. As long as the productW is set in the above range, one or two persons can split the uppernozzle/plate integral unit using a crowbar.

As above, the upper nozzle/plate integral unit of the present inventionmakes it possible to manage a joint thickness between the upper nozzleand the upper plate to eliminate the risk of molten metal leakage andabnormal refractory wear, so as to achieve a stable casting operation.In addition, the upper nozzle/plate integral unit can be split into theupper nozzle and the upper plate to reduce the time and effort requiredfor detaching the upper plate from the molten metal vessel. The uppernozzle/plate integral unit installed in the detachable-type slidingnozzle assembly allows the upper nozzle to be mounted to the moltenmetal vessel in conjunction with an operation of attaching thedetachable-type sliding nozzle assembly to the molten metal vessel, soas to achieve enhanced operating efficiency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram for explaining a weld leg and a weldlength.

FIG. 2 is a front sectional view showing an upper nozzle/plate integralunit according to a first embodiment of the present invention.

FIG. 3 is a top plan view of the upper nozzle/plate integral unit inFIG. 2.

FIG. 4 is a perspective view showing an upper nozzle/plate integral unitaccording to a second embodiment of the present invention.

FIG. 5 is a perspective view for explaining an operation of detaching adetachable-type sliding nozzle assembly having an upper nozzle/plateintegral unit of the present invention, from a tundish.

FIG. 6 is a sectional view for explaining one example of a method ofsplitting an upper nozzle/plate integral unit of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described based on an embodiment thereof.

First Embodiment

An upper nozzle/plate integral unit according to a first embodiment ofthe present invention will be shown as one example where a metal casingwhich covers an outer peripheral surface of an upper nozzle is used as“a metal member provided on a lower end portion of an upper nozzle”, anda metal sheet which covers an upper surface of an upper plate is used asa “metal sheet provided on an upper surface of an upper plate”.

FIG. 2 is a front sectional view showing the upper nozzle/plate integralunit according to the first embodiment, and FIG. 3 is a top plan view ofthe upper nozzle/plate integral unit.

In FIGS. 2 and 3, the reference numeral 10 indicates the uppernozzle/plate integral unit which comprises an upper nozzle 1 and anupper plate 2 adapted to be fitted into a lower end portion of the uppernozzle 1, and the reference numeral 3 indicates a nozzle hole.

The upper nozzle 1 is a generally cylindrical-shaped refractory memberhaving a nozzle hole 3. The upper nozzle 1 has a metal casing 4 which isformed to have a thickness of 0.8 mm and provided to cover an outerperipheral surface of an intermediate portion and the lower end portionthereof, except an upper end portion.

As shown in an enlarged view of the circled region in FIG. 2, a gapbetween the upper nozzle 1 and the metal casing 4 is filled with mortar5.

As shown in FIG. 3, the upper plate 2 is a rectangular plate-shapedalumina carbon-based refractory member having a nozzle hole 3 and acutout in each corner. The upper plate 2 has a metal band 7 which isformed to have a thickness of 3 mm and provided on a lateral surfacethereof, and a metal sheet 8 which is formed to have a thickness of 3 mmand provided on an upper surface of the upper plate 2 while beingweldingly fixed to the band 7. The metal sheet 8 has a circular-shapedcutout concentric with a raised portion 21 of the upper plate 2, and acylindrical portion 9 formed around the cutout. The cylindrical portion9 is formed to have a thickness of 3 mm.

The lower end portion of the upper nozzle 1 has a recess 11 formed in abottom surface thereof and fitted onto the raised portion 21 of theupper plate 2 through mortal 5 as a joint material. A portion of themetal casing 4 on an outer peripheral surface of the lower end portionof the upper nozzle 1 is fixedly joined to the cylindrical portion 9 ofthe metal sheet 8 through four welded portions 6. The mortar 5 in thefitting region between the raised portion 21 and the recess 11 has athickness of 3 mm. This joint thickness can be reliably managed bymeasuring a joint thickness around the nozzle hole 3 using a measuringinstrument after welding. Each of the four welded portions 6 has a weldleg of 3 mm, and a weld length of 4 mm. Thus, a total weld length is 16mm.

An upper nozzle/plate integral unit different only in weld length fromthat in FIG. 3 was subjected to a weld split/break test. As a result, anupper nozzle/plate integral unit having a weld leg of 3 mm, a weldlength of 8 mm and a total weld length of 32 mm (a product W of the weldleg S and the total weld length L2 is 96) was split at 3.4 t, and anupper nozzle/plate integral unit having a weld leg of 3 mm, a weldlength of 15 mm and a total weld length of 60 mm (the product W of theweld leg S and the total weld length L2 is 180) was split at 4.7 t.

Second Embodiment

FIG. 4 is a perspective view showing an upper nozzle/plate integral unitaccording to a second embodiment of the present invention.

The upper nozzle/plate integral unit according to the second embodimentwill be shown as one example where a metal band attached onto an outerperipheral surface of a lower end portion of an upper nozzle is used asthe “metal member provided on a lower end portion of an upper nozzle”,and a metal casing which covers an upper surface of an upper plate isused as the “metal sheet provided on an upper surface of an upperplate”.

An upper nozzle 1 has a metal band 7 which is formed to have a width of30 mm and a thickness of 1 mm, and attached onto an outer peripheralsurface of a lower end portion thereof to serve as the metal member.

The band 7 has a convex portion (not shown) formed on an inner surfacethereof and adapted to be fitted into a concave portion (not shown)formed in the outer peripheral surface of the upper nozzle 1 so as tofacilitate retaining therebetween. Further, the band 7 and the uppernozzle 1 are joined together by filling a gap therebetween using mortarwith a high bonding force.

An upper plate 2 has a metal casing 4 which is formed to have athickness of 1.6 mm, and provided to cover a lateral surface and anupper surface (except a raised portion) thereof.

A lower end of the band 7 attached onto the outer peripheral surface ofthe lower end portion of the upper nozzle 1 is fixed to the metal casing4 through four welded portions 6. Each of the four welded portions 6 hasa weld leg of 2 mm, and a weld length of 4 mm. Thus, a total weld lengthis 16 mm.

Third Embodiment

A method of splitting the upper nozzle/plate integral unit according tothe first or second embodiment will be described based on one examplewhere a detachable-type sliding nozzle assembly having the uppernozzle/plate integral unit is attached to a tundish. More specifically,an operation of detaching a used detachable-type sliding nozzle assemblyfrom a tundish to replace it with a detachable-type sliding nozzleassembly having new refractory members will be described below.

Although not illustrated, a detachable-type sliding nozzle assembly 100in FIG. 5 comprises the upper nozzle/plate integral unit as shown inFIG. 2, an intermediate plate, a lower plate and a lower nozzle, whichare housed in a metal frame, and adapted to be detachably attached to abottom of a tundish together with the metal frame.

The sliding nozzle assembly 100 illustrated in FIG. 5 is fixedlyattached to a tundish (not shown) by fastening a fixing bracket (notshown) provided on a lateral surface of the assembly to a bolt providedon a shell (not shown) of the tundish, using a nut.

The sliding nozzle assembly 100 has two splitting brackets 20 providedon respective ones of opposed longitudinally-extending lateral surfacesthereof, and a hydraulic ram cylinder 30 having an output of 5 t offorce is detachably attached to each of the splitting brackets 20.

In an operation of detaching the above sliding nozzle assembly 100, ahook of a crane is attached to an upper portion of the sliding nozzleassembly 100, and then the fixing between the tundish and the slidingnozzle assembly 100 is released by loosening the nut fastened to thebolt provided on the shell of the tundish. Subsequently, the slidingnozzle assembly 100 is hung by the crane, and the hydraulic ramcylinders 30 are attached to the respective brackets 20 in such a manneras to be interposed between the tundish and the sliding nozzle assembly100.

Then, a hydraulic pressure of the hydraulic ram cylinders 30 isincreased to break the welded portions between the upper nozzle and theupper plate by a hydraulic driving force of the hydraulic ram cylinders30. In this embodiment, the welded portions between the upper nozzle andthe upper plate can be broken when the output force of the hydraulic ramcylinders 30 is in the range of 1 to 2 t. Subsequently, the upper nozzleleft in the tundish can be detached in such a manner that it is pulledout from outside the tundish or pushed out from inside the tundish.

Fourth Embodiment

A method of splitting the upper nozzle/plate integral unit according tothe first or second embodiment will be described based on one example ofan operation of replacing a refractory member in an on-site mannerwithout detaching the entire upper nozzle/plate integral unit from atundish.

FIG. 6 is a sectional view for explaining the operation. In thisexample, a retaining metal frame 12 has a concave portion for receivingtherein the upper plate 2, and the concave portion is formed with agroove 13.

In an operation of detaching the upper plate 2 from a tundish after use,a crowbar 14 is manually inserted into the groove 13, and moved to scoopout the upper plate 2 so as to break welded portions based on theprinciple of leverage to split the upper nozzle/plate integral unit intothe upper nozzle 1 and the upper plate 2. Then, the upper nozzle 1 canbe pulled out using a hydraulic power unit or the like.

In this embodiment, the upper nozzle/plate integral unit has threewelded portions, wherein a weld leg is 3 mm, and a total weld length is9 mm. In this case, one adult person can split the upper nozzle/plateintegral unit into the upper nozzle and the upper plate byhimself/herself, using a crowbar having a length of 1 m.

1. An upper nozzle/plate integral unit capable of being split into anupper nozzle and an upper plate and detached from a molten metal vessel,after use, wherein: said upper nozzle is in contact with said upperplate through a joint material, in such a manner that respective nozzleholes of said upper nozzle and said upper plate are aligned with eachother; said upper nozzle has a metal member provided on a lower endportion thereof; and said upper plate has a metal sheet provided on anupper surface thereof, wherein said metal member of said upper nozzle isweldingly joined to said metal sheet of said upper plate at two or morepositions, in such a manner that a weld leg is set in the range of 2 to5 mm, and a total weld length is set in the range of 5 to 60 mm.
 2. Theupper nozzle/plate integral unit as defined in claim 1, wherein aproduct (W) of said weld leg (S [mm]) and said total weld length (L2[mm]) is set in the range of 25 to
 300. 3. The upper nozzle/plateintegral unit as defined in claim 1 or 2, which is installed in adetachable-type sliding nozzle assembly.
 4. A method of splitting theupper nozzle/plate integral unit as defined in claim 3, comprising:interposing a hydraulic ram cylinder between the detachable-type slidingnozzle assembly and the molten metal vessel; and moving said hydraulicram cylinder in such a manner that said detachable-type sliding nozzleassembly is detached from said molten metal vessel while splitting saidupper nozzle/plate integral unit into said upper nozzle and said upperplate.
 5. A method of splitting the upper nozzle/plate integral unit asdefined in claim 1 or 2, comprising: providing a retaining metal frameformed with a concave portion having a crowbar insertion groove; andinserting a crowbar into said crowbar insertion groove, and moving saidcrowbar to scoop out said upper plate, so as to split said uppernozzle/plate integral unit into said upper nozzle and said upper plate.